Abstract
The therapeutic potential of plant extracts has attracted significant interest, especially regarding indigenous species with health-promoting properties. Gymnema inodorum, native to Northern Thailand, is recognized for its rich phytochemical profile; however, the impact of various extraction techniques on its phenolic composition and bioactivity remains underexplored. Optimizing extraction methods is essential to enhance the pharmacological efficacy of this plant's bioactive compounds. This study investigated the influence of four extraction methods-ethanol maceration, ethanol reflux, aqueous decoction, and microwave-assisted extraction-on the bioactive profile of G. inodorum leaves, with a focus on the phenolic content and biological activities. Antioxidant activities were evaluated using DPPH, ABTS, and FRAP assays, while the total phenolic and flavonoid contents were quantified by colorimetric methods. High-Performance Liquid Chromatography (HPLC) quantified gymnemic acid and key phenolic compounds. Among the methods, ethanol reflux yielded the highest antioxidant activities (DPPH and ABTS scavenging), with a total phenolic content of 82.54 mg GAE/g and flavonoid content of 31.90 mg QE/g. HPLC analysis identified sinapic acid, myricetin, and p-hydroxybenzoic acid as major phenolics. Furthermore, the ethanol reflux extract displayed potent anti-diabetic activity, with IC(50) values of 13.36 mg/mL for α-amylase and 7.39 mg/mL for α-glucosidase, as well as strong anti-inflammatory activity (IC(50) of 1.6 mg/mL) and acetylcholinesterase inhibition (IC(50) of 1.2 mg/mL). These findings suggest that ethanol reflux extraction is a highly effective method for producing bioactive-rich G. inodorum extracts, with substantial pharmacological potential for developing herbal remedies and nutraceuticals, particularly in enhancing therapeutic approaches for diabetes and other health-related conditions.